About a month after Attorney General Jeff Sessions announced that the government would implement a zero-tolerance policy on immigrants entering the country illegally — a decision central to the spiking number of cases of migrant children being separated from their parents — President Trump berated Homeland Security Secretary Kirstjen Nielsen during a Cabinet meeting.

Why, Trump wanted to know, didn’t Nielsen have solutions for the rising number of people apprehended trying to cross the border illegally? “How is this still happening?” he asked.

Central to that increase was a rise in the number of families caught at the border with Mexico. In February, 5,475 family units were apprehended at the border. In March, that rose to 8,873. In April, it was up to 9,653. In early April, Sessions made his zero-tolerance announcement, and White House Chief of Staff John F. Kelly told NPR later that month that the policy had a specific intent.

“Are you in favor of this new move announced by the attorney general early this week, that if you cross the border illegally even if you’re a mother with your children, to arrest you?” NPR’s John Burnett asked. “We’re going to prosecute you, we’re going to send your kids to a juvenile shelter?”

“They’re coming here for a reason,” Kelly said of migrants fleeing violence in Central America. “And I sympathize with the reason. But the laws are the laws. But a big name of the game is deterrence.”

Family separation would be a tough deterrent, Burnett noted.

“It could be a tough deterrent — would be a tough deterrent,” Kelly replied.

It wasn’t Kelly’s first time making the case that separating children from their families could deter immigrants from illegally seeking entry to the United States. When he held Nielsen’s job last year, he told CNN’s Wolf Blitzer that he was considering the policy as a deterrent.

“Let me start by saying I would do almost anything to deter the people from Central America to getting on this very, very dangerous network that brings them up through Mexico to the United States,” Kelly said.

Blitzer pressed him on the point: Is the Department of Homeland Security going to separate children from their parents?

“Yes, I am considering, in order to deter more movement along this terribly dangerous network, I am considering exactly that,” Kelly said. “They will be well cared for as we deal with their parents.”

Even in March 2017, the idea was not new. Two weeks after Trump was inaugurated, a DHS official named John Lafferty raised the idea of using family separation as a deterrent in a town hall meeting for Citizenship and Immigration Services officials, according to documents obtained by NBC News.

Once Kelly left DHS to join the White House in July, the hunt for deterrent policies continued. During an August meeting, the New Yorker reported, a DHS official named Gene Hamilton told DHS officials “that over the next few days we’d need to generate paperwork laying out everything we could do to deter immigrants from coming to the U.S. illegally,” one person said. Family separations reportedly were included in the mix.

Even over the past 24 hours, multiple administration officials have pointed to a possible deterrent effect in defense of the policy.

“General Sessions, is this policy in part used as a deterrent?” she asked. “Are you trying to deter people from bringing children or minors across this dangerous journey? Is that part of what the separation is about?”

“Fundamentally, we are enforcing the law,” Sessions replied. “If you break into the country …”

“But is it a deterrent, sir?” Ingraham interjected. “Are you considering it a deterrent?”

“I see that the fact that no one was being prosecuted for this was a factor in a fivefold increase in four years in this kind of illegal immigration,” Sessions said. “So, yes, hopefully people will get the message and come through the border at the port of entry and not break across the border unlawfully.”

On a conference call with reporters on Tuesday morning, HHS’s acting assistant secretary, Steven Wagner, was explicit, according to a transcript provided to The Post by CNBC’s Christina Wilkie.

“We are staying one step ahead of the need,” Wagner said. “We expect that the new policy will result in a deterrence effect, we certainly hope that parents stop bringing their kids on this dangerous journey and entering the country illegally. So we are prepared to continue to expand capacity as needed. We hope that that will not be necessary in the future.”

HuffPost reports that using family separation as a deterrent may be legally questionable. Either way, the policy has prompted several questions about ethics.

Nielsen was asked about the policy on Monday afternoon at the White House.

“Are you intending for parents to be separated from their children?” a reporter asked. “Are you intending to send a message?”

“I find that offensive,” Nielsen replied. “No. Because why would I ever create a policy that purposely does that?”